The present invention relates to a fine patterning method using an X-ray and a mask and, more particularly, to a technique for making a pattern with great accuracy by reducing the secondary electrons generated in accordance with the exposure to the X-ray.
In the lithography using radiation, especially in the X-ray lithography, it is known in the art that the secondary electrons generated from an absorber of an X-ray mask are generated in a diverging form to act upon a resist thereby reducing the line width accuracy of a resist pattern. One example of counter measures against this reduced accuracy is disclosed in the Japan Journal of Applied Physics, Vol. 20 (1981), pp. 20 to 24.
However, no report has been found regarding the influence of secondary electrons which come from a layer to be transferred or a substrate to be worked in accordance with the exposure to the X-ray.
The worst defect of X-ray lithography for transferring a mask pattern to a layer by using the X-ray is that an absorber constructing the X-ray mask, a resist constructing the layer, a layer to be transferred, a substrate and so on absorb the X-ray, while they are being exposed to the X-ray, to emit secondary electrons such as photoelectrons or Auger electrons, which act upon the resist to degrade the accuracy of a transfer pattern. As a method of solving that problem, there is disclosed in "Submicron pattern replication using a high contrast mask and two-layer resist in X-ray lithography" by Y. Saitoh et al (J. Vac. Sci. Technol. Vol. B2 (1), Jan.-Mar. 1984, pp. 63 to 67) a method of absorbing secondary electrons by applying a high-molecular, film to the mask or the layer to be worked. In order to form a highly accurate pattern, however, the formation of that high-molecular film may have subsidiary defects due to either an increase in the film thickness or irregularities that reduce productivity.